Refining of rosin esters



Patented Mar. 16, 1943 UNITED STATES PATENT OFFICE REFINING OF ROSIN ESTERS William N. Traylor, Hattiesburg, Miss., assignor to Hercules Powder Company, "Wilmington, -Del., a corporation-ofDelaware N0 Drawing. Application April 18, 1941, .Serial N0. 389,177

12 Claims. (01. 260-103) This invention relates to rosin esters and more "particularly to, a process ,for refining rosin esters.

,Rosinesters have become very important commercially because of certain advantages which they 'TDQSSBSS over raw and hardened rosins. 'being substantially neutral, and covering :a wide range of other propertiesgoverned; by the particular:alcoholwwith which therosin is ester- ;ified, theymay :be extensively used :in ,fields such as the varnish zindustryin'which the high acidity :and limitedrangesof other; properties of raw and hardened 'rosins maybe undesirable.

However, the preparation of the especially valuable pale-colored rosin esters has been difficult in materials and equipment andmay change the properties of the ester.

"It is an object of this invention :to provide an improvedmethod-of refining rosin esters.

It is a further objectto :provide a process for :refiningrosin esters which will provide l a refined product in substantially quantative yield based on the rosin ester treated.

It is a-still further object -to provide a process for refining rosinesters which'iseXtr-emely simple and economical.

Another object of this invention is toprovide 'a process for refining rosin esters'which will :not substantially alter the properties of the rosin esters treated otherthan color.

Other objects-of the invention will appearhere inafter.

"The objects of this invention, in general, are accomplished by treating rosin esters with nascent hydrogen. The treatment is carried out under conditions which will provide intimate contact between the resin esters and the nascent hydrogen. As a result, the color of the rosin esters becomes substantially lightened "with practically no loss in yield and no perceptible effect onthe other physical properties.

In'accordancewiththe process of this invention the treatment maybe carried out on therosin esters in the molten condition or itmay becar- -ried=out=on-the rosin esters dissolvedin a suitable are suitable.

organic solvent. ,Afterthetreatment of the rosin esters iscompleted, the rosin esters or the solu- .tion of rosin esters may be washed to remove any water-soluble materialandfiltered to remove any suspended matter. ,In the case .of treatment of ,the rosinesters insolution, the rosin esters of improved color may then be recovered by evaporationof the solvent.

The .process of this invention is applicable to any of the various types of rosin esters or mixtures thereof. Thus, the esters of wood rosin .gum rosin-or heat treated or polymerized rosin with mono-,oripolyhydricaalcoholsmay be used in "the process of the invention. For example, rosin esterspf monohydric alcohols such as methyl,

ethyl, qamyl, stearyl, abietyl, and hydrogenated -abietyl alcohols, "or, ethylene glycol monoethyl ether or dihydric alcohols as ethylene glycol, 1 diethylene glycol, or polyhydric alcohols such as glycerin, diglycerin, pentaerythritol or mannltol Rosin 1esters produced by any of the usualmethods such as esterification at high temperatures with or without catalysts such as benzene sulfonic acid, zinc, .-etc., are suitable.

As solvents -for the i-rosin esters where the treatment is carried out on the rosin esters in solution, any solvent-for the rosin esters which is itself inertin. the-treatment may be employed.

Among "such solvents are, for example, monocyclic aromatic hydrocarbons, such as benzol,

toluol, -xylol, etc. petroleum hydrocarbons such'as gasoline, -V. M. {and P. :naphtha, hexane,-heptane,

etc:; hydrogenated petroleum hydrocarbonaisuch mas-those known in the :trade as Solvesso solvents; and solvents such as ethylene dichloride, "carbon tetrachloride, .cyclohexane, methyl-cyclohexane, tetrahydro and decahydronaphthalenes,

etc. Where ithe treatment-is carried outon the rosin-estersinsolution, the concentration of the 'rosin iesters in solution is notncritical and may be selected so as -'to i provide adequate "workability. :of

the-solution. In lgeneral a concentration within the range ofabout "10'to about '15 "byweight may be used, but preferably the concentration is held within the range of about 30% to*=50% by weight. If desired, :where rosin esters :are refined in the molten-state, solvent may bera'dded after the refining step to aid in theseparation of the refining agentf-rom the rosinresters'or in the-water washing ofsthe' esters.

The nascent'hydrogenyfor use tion may wbe derived -by anyof the well-known procedures for generating nascent hydrogen.

: Preferab1y, the, nascent hydrogen may be D 7 in the treatment of the rosin ester in accordancewith this invenvided by the reaction of an acid reactant 'with a metal above hydrogen in the electromotive series. The acid reactant may be either an acid or an acid salt or a mixture thereof. .Among the acid reactants which may be used are, for example, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, sodium acid sulfate, potassium acid sulfate, monosodium acid phosphate, calcium acid phosphate, etc. The preferred acid reactants are the acid salts, sodium acid sulfate being particularly effective.

Any of the metals above hydrogen in the electromotive series may be employed. It will be preferable, however, to use such metals which form salts having no appreciable discoloring action on the rosin esters. The metals are used preferably though not necessarily in a finely divided form. Use of metals such as, for example, cadmium, aluminum, manganese, tin, and zinc is very desirable. Zinc in the form of zinc dust,

mossy zinc, or zinc'powder is particularly well adapted to the process. It will be desirable that at least 'a small amount of water or of some other ionizingLsolvent be present to accelerate the refining action. :Use of an aqueous acid or of the hydrate of an acid salt will provide the desired ionizing effect; It will be understood that the acid reactant and the metal are both in contact with the rosin esters during the treatthen be passed through the cell for the length of'time dependenton the current and the degree of refining desired. 1

It is desirable to employ vigorou agitation in carrying out the treatments to obtain thorough contact "of thereactants and to accelerate'the refining action. The speed with which the rosin esters become refined'is also dependent on the temperature employedin the treatment. While thetreatment'may be carried out at room temperaturewith the rosin esters dissolved in a suitable solvent, the rate of refining is rather slow for practical purposes.

It is preferable to carry out the treatment at elevated temperatures and temperatures as high as 200 C. have'been found to be satisfactory although higher'temperatures are possible. A temperature within the range of about 70 C. to about 125 C. is preferable. When carrying out the treatment of the rosin esters in solution,.it is convenient to carry out the treatment at the reflux temperature of the solvent. Where the treatment is'to be carried outabove the normal boiling point of the solvent,

= use of superatmospheric pressure is resorted to. The pressures employed are in no. way limiting onfthe process, and the equipment employed will generally determine the maximum pressure which i's practical.

The time of treatment of the rosinesters may be varied to produce the result desired' The time'nefcessary to provide satisfactory refining of the rosin esters will be dependent on such factors as the amount of color bodies present in' the rosin ester, the temperature of treatment, the

amount of nascent hydrogen utilized, etc. For

reason, it is impossible to state any definite time necessary, except in relation to a given set ofconditions. "The examples given. hereinafter will serve to illustrate the kind of treatment which may be used in any particular case.

The amount of acid reactant used for producing nascent hydrogen, when this method of gencrating nascent hydrogen is employed, may vary over a wide range, depending on such factors as the particular acid reactant used, the degree of refining desired, the particular conditions of treatment, as well as other factors. Assuming the acid reactant tobe on an anhydrous basis, ratios of rosin ester to acid reactant as high as 40 to 1 on a weight basis have been used. In general, however, ratios varying between 10 of rosin ester to 1 of acid reactant down to l of rosin ester to l of acid reactant are desirable. A preferred ratio is approximately 3 of rosin ester to l of acid reactant.

The concentration of the acid reactant in terms of ionizing solvent may also be widely varied, for example, sulfuric acid may be used as the acid reactant in concentration of from3% to 60% in aqueous solution, while acetic acid may be used in the substantially anhydrous form of glacial acetic acid, as well as in an aqueous solution. When acids are used as the acid reactants, however, concentrations of acid of 20 to 50% are generally preferable. When using acid salts as acid reactants, a hydrate or an aqueous solution 7 from a concentration of about 5% by weight to a saturated solution may be employed. The monohydrate of sodium acid sulfate, for example, is

a particularly efiective acid reactant in the process according to the invention.

The amount of metal above hydrogen in the electromotive series which is employed is not particularly critical. It will be preferable, however, to have such an amount of metal present which will be an excess over the theoretical amount required to react with the acid reagent 40 present. I

The process of refining rosin esters in accordance with this-invention may also be carried out as a continuous'process if desired; Thus, for example, the rosin ester solution may be treated with the acid reactant and the metal above hydrogen in the electromotive series in'a suitable V vessel while additional rosin ester solution is fed into the vessel continuously and refined rosin estersolution withdrawn from the vessel at substantially the same rate. The acid reactant and metal may be replenished as necessary and the refined solution passed to 'a continuous evaporator for removal of the solvent.

The use of an inert atmosphere such as ,Nz or 002 during the various refining stepsis often of assistance in obtaining pale colors. This may be particularlyhelpful during washing of treated rosin ester solutions or in the evaporation of solvents therefrom.

fining rosin esters in accordance with this invencolors measured on 7 cubes of the rosin esters.

EXAMPLE I A nearly black crude methyl abietate obtained by high temperature direct esterification of rosin with methyl alcohol was refined with various treating agents. Solutions containing 62 parts by weight of this ester and 190 parts by weight of solvent were refluxed separately for one hour with the parts by weight of refining agents as shown in Table I below. Each treated solution As illustrative of the improved process of re- 7 after cooling was decanted, washed 'withwater, tfiltered to. remove metal remaining, and therosin ester then recovered by distilling olf .the'solvent .in vacuo. There was no loss of material inthe What *Iblaimmnd "desireto protect =by 'hetters Patent is:

1. Aiprocessfor refining aros'in ester'which comprisestreating saidrosin ester with-nascent It is to be understood that the term refining used throughout this invention refers particulary to the color improvement of the rosin esters and not necessarily to a separation of the rosin esters into light-colored and dark-colored fractreatment. "'hydrogenin the "presence of 'anacidic"reactant "Table I h Treating agent ggi f f v Solvent U. gfgigg g Lovibond color Metal Acidi'eaetant 1 n 20 parts. Z11 powderm". 30 parts NaHSOnHzOQ. Benzene 22 b 2 3Q parts he powder 'aofiigi rts-aqueous do r. i i 55 b i 3 w- .20,partsZn powdermlQ. :50 parts .glacial acetic do so mb r-H125 red .:4 r mpartSTSn mossy "i5ofipcalrts aqueous 40% Ethylenedichloridc... G+ -80amber+8..red.

EXAMPLE II V Fifty parts by of the nearly black crude ;.containing ionizable,rihyd-rogen andtin the :.D1 esmethyl abietate of Example I was agitated with enceofrattleasta:smallamount ,ofcwater.

a mixture of 7.5 parts by weight of zinc powder process fi rosm e.ster whlqh and 105 parts by weight of sodium acid sulfate compnses treating ester dlssolved m monohydrate for one-half hour at a temperature Smtable solvent wi nascent hydrogep m.the 120C 5 presence of an acidic reactant containing ion- After cooling the rosin ester was extracted Mable hydrogen and in the presence'of least with 175 parts of toluene. The rosin ester so- 2x53111321 1222; t gzg a m t h lution was then filtered to remove small amounts p n Sm i er w of dispersed zinc and the solvent removed from comprises treating said rosin ester with nascent i the filtered solution under reduced pressure. The hydl ogen t p b t reactlon of an acldm refined methyl abietate graded M U. S. Standard actant contammg wmzable hydmgel} and metal rosin type or 45 Amber Lovibomi Colon above hydrogen in the electromotive series in contact with said rosin ester and in the presence EXAMPLE III of at least a small amount of water.

An ester gum prepared by esterification of WW D efi & os n ster which gum rosin with glycerin and having a color I, a, comprises treating said rosin ester dissolved in a melting point of 105 C. and an acid number of 6 sultable o v l e n yd ogen formed by was refined with several types of treating agents. the reaction of an acidic reactant containing 1on- Solutions containing 62 parts by weight of the 40 a l hy r e an a al above y n 1n ester gum and 190 parts by weight of solvent were the electromotive series in contact with the rosin refluxed separately over the refining agent for ester solution and in the presence of at least a one hour. The ester was recovered as in Exsmall amount of water. ample I, and with no loss of material in the 5. A process for refining a rosin ester which treatment. A table showing the type and parts comprises treating said rosin ester dissolved in a. by weight of treating agent, and solvent, and the suitable solvent with nascent hydrogen formed by color of the refined ester gum for each treatment the reaction of an acid and a metal above hydrofoll w gen in the electromotive series in contact with the Table II Treating agent SHNEBDIQ Solvent U gfigg g g Lovibond color Metal Acid reactant 1 20 parts Zn powder 30 parts NaHSO4.HQO B m n WG+ 24amber,

2; 20 parts Fe powder 30HpCa1rts aqueous 10% do 1+ 80 whe 3 10 parts Zn powder. parts glacial acetic do M 45 amber.

4 20parts Sn mossy 5oH glrts aqueous 10% Ethylene dichloride--- K amber,

5 20parts Zn powder GOH arts aqueous 10% Ethylene dichloride WW 22 amber; e 20 parts Sn powder so r i r'ts aqueous 10% M 45 amber.

7 20parts Zn powder GUHDSIgS aqueous 40% Narrowrangegasoline- M De. i 2 4- rosin ester solution and in the presence of at least a small amount of water.

6. A process for refining a rosin ester which comprises treating said rosin ester dissolved in a suitable solvent with nascent hydrogen formed by the reaction of a metal above hydrogen in the electromotive series and an acid salt in contact with the rosin acid solution and in the presence of at least a small amount of water.

7. A process for refining a rosin ester which comprises treating said rosin ester dissolved in a suitable solvent with nascent hydrogen formed by the reaction of sodium acid sulfate and a metal above hydrogen in'the electromotive series in contact with the rosin ester solution and in the presence of at least a small amount of water.

8, A process for refining a rosin ester which comprises treating said rosin ester dissolved in a suitable solvent with nascent hydrogen formed by the reaction of an acidic reactant containing ionizable hydrogen and zinc in contact with the rosin ester solution and in the presence oi at least a small amount of water.

9. A process for refining a rosin ester which comprises treating said rosin ester dissolved in a by the reaction of zince and sodium acid sulfate monohydrate in contactwith the rosin ester solution and in the presence of at least a small amount of water. 7 V r 11. A process for refining a rosin ester which comprises treating said rosin ester dissolved in a suitable solvent with nascent hydrogen formed by the reaction of an acidic reactant containing ionizable hydrogen and a metal above hydrogen in the electromotive series in contact with the rosin ester solution, at a temperature within the range of about 70 to about 125 C. and in the presence of at least a small amount of water.

12. A process for refining a rosin ester which comprises treating said rosin ester dissolved in a suitable solvent with nascent hydrogen formed by the reaction of sodium acid'sulfate monohydrate V 20 to'about 125 C.

WILLIAM N. TRAYLOR, 

